Reciprocating saw

ABSTRACT

A reciprocating saw includes a housing, a motor, and a drive mechanism. The motor is configured to operate in a forward mode corresponding to a first rotational direction, and in a reverse mode corresponding to a second rotational direction opposite the first rotational direction. The drive mechanism includes a driven gear, a connecting rod, an output shaft, and a counterweight. The driven gear is rotated by the motor and has an upper portion and a lower portion. The output shaft reciprocates through a cutting stroke and a return stroke. The counterweight is coupled to the driven gear and rotating with the driven gear. When the motor is operated in the forward mode, the counterweight moves through the upper portion of the driven gear during the cutting stroke of the output shaft, and moves through the lower portion of the driven gear during a return stroke of the output shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 16/422,189, filed May 24, 2019, which is a continuation of U.S. patent application Ser. No. 15/723,815, filed Oct. 3, 2017, now U.S. Pat. No. 10,300,541, which is a continuation of U.S. patent application Ser. No. 14/296,892, filed Jun. 5, 2014, now U.S. Pat. No. 9,776,263, which is a continuation-in-part of U.S. patent application Ser. No. 12/842,209, filed Jul. 23, 2010, now U.S. Pat. No. 9,579,735, and which claims priority to U.S. Provisional Patent Application No. 61/831,968, filed Jun. 6, 2013, the entire contents of all of which are incorporated by reference herein.

BACKGROUND

The present invention relates to power tools and, more particularly, to reciprocating saws.

Power tools include different types of drive mechanisms to perform work. Power tools with reciprocating-type drive mechanisms commonly include counterweights to counterbalance forces generated by output elements (e.g., saw blades) during reciprocating movement. Due to the orientation of the counterweights within the power tools, however, movement of the counterweights may generate inertia that tends to move the power tools away from work pieces while the power tools are operating.

SUMMARY

In one embodiment, the invention provides a reciprocating saw including a housing and a motor positioned within the housing. The motor is configured to operate in a forward mode and in a reverse mode, the forward mode corresponding to rotation of the motor in a first rotational direction, and the reverse mode corresponding to rotation of the motor in a second rotational direction opposite the first rotational direction. The reciprocating saw also includes a drive mechanism positioned within the housing and coupled to the motor. The drive mechanism includes a driven gear that is rotated by the motor. The driven gear is vertically-oriented within the housing and has an upper portion and a lower portion. The drive mechanism also includes a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, and an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke. The output shaft is configured to support a tool element. The drive mechanism further includes a counterweight coupled to the driven gear and rotating with the driven gear. When the motor is operated in the forward mode, the counterweight moves through the upper portion of the driven gear during the cutting stroke of the output shaft, and moves through the lower portion of the driven gear during the return stroke of the output shaft.

In another embodiment, the invention provides a reciprocating saw including a housing and a motor positioned within the housing. The motor includes a pinion, and the motor is configured to operate in a forward mode and in a reverse mode. The forward mode corresponds to rotation of the motor in a first rotational direction, and the reverse mode corresponds to rotation of the motor in a second rotational direction opposite the first rotational direction. The reciprocating saw further including a rotation direction reversal switch supported by the housing and coupled to the motor. The rotation direction reversal switch operable to selectively switch the motor between the forward mode and the reverse mode. The reciprocating saw further includes a drive mechanism positioned within the housing and coupled to the motor. The drive mechanism includes a driven gear that engages the pinion and is rotated by the motor. The driven gear is vertically-oriented within the housing. The drive mechanism also includes a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, and an output shaft coupled to the connecting rod to reciprocate relative to the housing and configured to support a tool element. The drive mechanism further includes a counterweight coupled to the driven gear and rotating with the driven gear.

In another embodiment, the invention provides a method of operating a reciprocating saw. The reciprocating saw includes a housing, a motor positioned within the housing and configured to operate in a forward mode and in reverse mode, a rotation direction reversal switch supported by the housing and coupled to the motor, and a drive mechanism positioned within the housing and coupled to the motor. The drive mechanism includes a driven gear that is rotated by the motor and vertically-oriented within the housing, a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke, and a counterweight coupled to the driven gear and rotating with the driven gear. The method includes operating the reciprocating saw with the motor set in the forward mode, actuating the rotation direction reversal switch to set the motor in the reverse mode, and operating the reciprocating saw with the motor set in the reverse mode.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a reciprocating saw embodying the invention.

FIG. 2 is a side view of the reciprocating saw with a portion of a housing removed.

FIG. 3 is a top view of the reciprocating saw with a portion of the housing removed.

FIG. 4 illustrates a saw blade for use with the reciprocating saw.

FIG. 5 is a graph depicting vertical vibration caused by a counterweight moving in accordance with the present invention.

FIG. 6 is a graph depicting vertical vibration caused by a counterweight moving in an opposite direction than the present invention.

FIG. 7 is a perspective view of another reciprocating saw.

FIG. 8 is a schematic of a control mechanism of the reciprocating saw of FIG. 7.

FIG. 9 is a graph depicting measured cut times of the reciprocating saw of FIG. 7 and of a conventional reciprocating saw, when cutting wood and metal workpieces.

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate a power tool 10. In the illustrated embodiment, the power tool 10 is a reciprocating saw. In other embodiments, the power tool 10 may be another type of device that utilizes a reciprocating-type drive mechanism, such as a jigsaw, a sabre saw, a hammer drill, or the like.

The illustrated reciprocating saw 10 includes a housing 14, a motor 18 positioned within the housing 14, and a drive mechanism 22 coupled to the motor 18 and positioned within the housing 14. As shown in FIG. 1, the housing 14 is comprised of two clamshell halves 24A, 24B that are connected together along a plane 25 (FIG. 3). In the illustrated embodiment, the clamshell halves 24A, 24B are secured together with threaded fasteners (e.g., screws), but may alternatively be secured together using other suitable coupling means. FIG. 2 illustrates the reciprocating saw 10 with one of the clamshell halves 24A removed to facilitate illustration of the internal components (e.g., the motor 18, the drive mechanism 22, etc.) of the saw 10.

Referring back to FIG. 1, the housing 14 includes a rearward portion 26, a forward portion 30, and a battery support portion 34. The housing 14 also defines a longitudinal axis 38 (FIG. 2) that extends through the rearward and forward portions 26, 30. The rearward portion 26 includes a D-shaped handle 42, and the forward portion 30 includes a grip 46. The D-shaped handle 42 and the grip 46 are configured to be grasped by a user during operation of the reciprocating saw 10. An actuator or trigger 50 is supported by the rearward portion 26 adjacent the D-shaped handle 42. The trigger 50 is actuatable by a user to selectively power the motor 18. In the illustrated embodiment, the trigger 50 is positioned above the longitudinal axis 38, and the longitudinal axis 14 generally divides the housing 14 into an upper section and a lower section. A shoe 54 extends from and is pivotally coupled the forward portion 30 of the housing 14. The shoe 54 pivots about a pivot axis 56 and facilitates aligning the reciprocating saw 10 on a work piece to be cut.

The battery support portion 34 is formed on the rearward portion 26 of the housing 14 below the D-shaped handle 42. In the illustrated embodiment, the battery support portion 34 is located beneath the longitudinal axis 38 of the housing 14 when the reciprocating saw 10 is viewed as shown in FIG. 2. In other embodiments, the battery support portion 34 may be located elsewhere on the housing 14. The battery support portion 34 is configured to receive a battery pack (e.g., an 18 volt Li-ion power tool battery pack) and electrically connect the battery pack to the motor 18. In other embodiments, the battery pack may have different voltages and/or chemistries. In still other embodiments, the reciprocating saw 10 may include a power cord such that the motor 18 is powered by an AC power source (e.g., a wall outlet, a portable generator, etc.).

As shown in FIG. 2, the motor 18 is positioned within the housing 14 between the rearward portion 26 and the forward portion 30. The motor 18 is also electrically connected to the battery pack (or other suitable power source) through the trigger 50. As shown in FIG. 3, the motor 18 includes a motor shaft 58 and an output gear or pinion 62. Referring back to FIG. 2, the motor shaft 58 defines a central longitudinal axis 70, or motor axis, of the motor 18. In the illustrated embodiment, the central longitudinal axis 70 of the motor 18 is generally aligned or coaxial with the longitudinal axis 38 of the housing 14. When powered, the motor 18 rotates the motor shaft 58 and the pinion 62 about the axis 70 to drive the drive mechanism 22.

As shown in FIGS. 2 and 3, the drive mechanism 22 is positioned at least partially within the forward portion 30 of the housing 14 between the motor 18 and the shoe 54. The illustrated drive mechanism 22 is a slider-crank mechanism that includes a driven gear 74, a connecting rod 78, and an output shaft 82. However, other mechanisms known in the art, such as a scotch-yoke mechanism, are also contemplated. The driven gear 74 engages the pinion 62 of the motor 18 and defines a central axis 86 about which the gear 74 rotates. In the illustrated embodiment, the central axis 86 is perpendicular to the longitudinal axis 38 of the housing 14, extends between opposing sides of the housing 14, and is parallel to the pivot axis 56 of the shoe 54. More particularly, the central axis 86 is perpendicular to the plane 25 along which the clamshell halves 24A, 24B of the housing 14 are connected. The driven gear 74 is thereby vertically-oriented within the housing 14.

The longitudinal axis 38 of the housing 14 and the central axis 70 of the motor 18 extend through a center of the gear 74 (i.e., through the central axis 86) to divide the gear 74 into a first, or upper, portion 90 and a second, or lower, portion 94. In the illustrated embodiment, the upper portion 90 of the driven gear 74 is located on the same side of the longitudinal axis 38 as the output shaft 82 and the trigger 50, while the lower portion 94 of the driven gear 74 is located on the same side of the longitudinal axis 38 as the battery support portion 34. In other embodiments, the output shaft 82 may be located on the opposite side of the longitudinal axis 38 such that the lower portion 94 of the driven gear 74 is located on the same side of the longitudinal axis 38 as the output shaft 38. It should be understand that what constitutes the upper and lower portions 90, 94 of the driven gear 74 changes during operation of the drive mechanism 22 because the gear 74 rotates. The terms “upper” and “lower” are simply illustrative terms used to help describe volumes of spaces above and below the axes 38, 70 that are occupied by sections of the gear 74 at any given time. At a particular instance in time, the actual section of the gear 74 that qualifies as the “upper portion” or the “lower portion” is different than at another instance in time.

The connecting rod 78, or drive arm, includes a first end that is coupled to the driven gear 74 by a crank pin 98 and a second end that is coupled to the output shaft 82 by a pivot pin 102. The crank pin 98 is offset from the central axis 86 of the driven gear 74 such that, as the gear 74 is rotated, the crank pin 98 moves about the central axis 86. As the first end of the connecting rod 78 moves with the driven gear 74, the second end of the connecting rod 78 pushes and pulls the output shaft 82 in a reciprocating motion. The crank pin 98 allows the connecting rod 78 to pivot vertically relative to the driven gear 74, while the pivot pin 102 allows the connecting rod 78 to pivot vertically relative to the output shaft 82.

The output shaft 82, or spindle, reciprocates within the forward portion 30 of the housing 14 generally along a spindle axis 106. In the illustrated embodiment, the spindle axis 106 is generally parallel to and positioned above the longitudinal axis 38 of the housing 14. Rotary motion of the motor 18 is thereby translated into linear reciprocating motion of the output shaft 82 by the driven gear 74 and the connecting rod 78.

The motor axis 70 and the spindle axis 106 together define a plane. The driven gear 74 is vertically-oriented within the housing 14 in that the gear 74 rotates about an axis (i.e., the central axis 86) that is perpendicular to the plane defined by the motor and spindle axes 70, 106. In the illustrated embodiment, the plane defined by the motor and spindle axis 70, 106 is the same as the plane 25 (FIG. 3) along which the clamshell halves 24A, 24B are coupled together. In other embodiments, one or both of the motor and spindle axes 70, 106 may be offset from, yet still parallel to the plane 25.

With continued reference to FIG. 2, a blade clamp 110 is coupled to an end of the output shaft 82 opposite from the connecting rod 78. The blade clamp 110 receives and secures a saw blade 112 (FIG. 4), or other tool element, to the output shaft 82 for reciprocating movement with the output shaft 82. The output shaft 82 supports the saw blade 112 such that, during operation of the reciprocating saw 10, the drive mechanism 22 moves the saw blade 112 through a cutting stroke when the output shaft 82 is pulled by the connecting rod 78 from an extended position to a retracted position, and through a return stoke when the output shaft 82 is pushed by the connecting rod 78 from the retracted position to the extended position.

The illustrated drive mechanism 22 also includes a counterweight 114. The counterweight 114 helps balance forces generated by the output shaft 82 and an attached saw blade during reciprocating movement. In the illustrated embodiment, the counterweight 114 and the driven gear 74 are separate elements, but may alternatively be integrally formed as a single piece. The illustrated counterweight 114 includes a connection portion 118 and a mass portion 122. The connection portion 118 is coupled to the connecting rod 78 via the crank pin 98. A guide pin 126 also extends from the connection portion 118 and engages an inner surface of the housing 14. The guide pin 126 supports the counterweight 114 within the housing 14 and defines an axis of rotation 130 of the counterweight 114. In the illustrated embodiment, the axis of rotation 130 of the counterweight 114 and the central axis 86 of the driven gear 74 are generally coaxial so that the counterweight 114 and the driven gear 74 rotate about the same axis. Similar to the driven gear 74, the counterweight 114 is, therefore, also vertically-oriented within the housing 14. In the illustrated embodiment, the axis of rotation 130 intersects and is perpendicular to the motor axis 70.

The mass portion 122 extends from the connection portion 118 and includes a majority of the mass of the counterweight 114. As such, movement of the mass portion 122 in a direction opposite the movement of the output shaft 82 tends to balance the forces generated during reciprocation of the saw blade in a front-to-back direction. In the illustrated embodiment, the mass portion 122 has a generally semi-circular shape to match the circular shape and contour of the driven gear 74. That is, the counterweight 114 is shaped and sized so it does not extend outside of (or only extends outside a minimal amount of) a vertical footprint area defined by the driven gear 74. Such an arrangement reduces the amount of space required within the housing 14 to accommodate the counterweight 114. In other embodiments, the mass portion 122 may have other suitable shapes or configurations.

As the driven gear 74 rotates and drives the crank pin 98, the mass portion 122 of the counterweight 114 is moved in a substantially opposite direction than the output shaft 82 to counterbalance the inertial forces of the output shaft 82 and attached saw blade. In particular, the mass portion 122 of the counterweight 114 is in a first position (e.g., relatively close to the motor 18 and relatively far from the output shaft 82), as shown in FIG. 2, when the output shaft 82 is in the extended position. The mass portion 122 of the counterweight 114 rotates to a second position (e.g., relatively close to the output shaft 82 and relatively far from the motor 18) when the output shaft 82 is in the retracted position.

In the illustrated embodiment, the counterweight 114 rotates along a path P in a clockwise direction R (when viewing the reciprocating saw 10 as shown in FIG. 2) about the axis of rotation 130 between the first and second positions. That is, the mass portion 122 of the counterweight 114 travels generally above the longitudinal axis 38 of the housing 14 and through the upper portion 90 of the driven gear 74 during the cutting stroke of the output shaft 82 to move from the first position to the second position. Conversely, the mass portion 122 of the counterweight 114 travels generally below the longitudinal axis 38 of the housing 14 and through the lower portion 94 of the driven gear 74 during the return stroke of the output shaft 82 to move from the second position to the first position. Stated another way, as the mass portion 122 of the counterweight 114 moves through a rearward half of the path P (i.e., the half of the path P that is closer to the rearward portion 26 of the housing 14) at the end of the return stroke and start of the cutting stroke, the mass portion 122 generally moves in an upward direction (as viewed in FIG. 2) and toward the spindle axis 106. As the mass portion 122 of the counterweight 114 moves through a forward half of the path P (i.e., the half of the path P that is closer to the forward portion 30 of the housing 14) at the end of the cutting stroke and start of the return stroke, the mass portion 122 generally moves in a downward direction (as viewed in FIG. 2) and away from the spindle axis 106. This movement of the counterweight 114 causes the front of the saw 10 to tend to move into a work piece (downward in FIG. 2) as the cutting stroke begins.

Because the counterweight 114 is coupled to the driven gear 74 by the crank pin 98, the counterweight 114 does not actually move relative to the gear 74. Instead, the counterweight 114 and the driven gear 74 rotate together through the path P. As discussed above, the terms “upper portion” and “lower portion” of the driven gear 74 refer to volumes of space occupied by sections of the gear 74 during operation of the drive mechanism 22.

The arrangement of the counterweight 114 and the driven gear 74 increases cutting performance of the reciprocating saw 10 compared with rotation of the counterweight 114 in the opposite direction (e.g., counterclockwise when viewing the reciprocating saw 10 as shown in FIG. 2). In particular, the mass portion 122 of the counterweight 114 tends to move the saw 10 in the cutting direction during the non-cutting stroke, which helps drive the reciprocating saw 10 and the saw blade 112 into the work piece at the start of the next cutting stroke. In contrast, if the counterweight 114 rotated in the opposite direction, the reciprocating saw 10 and the saw blade 112 may tend to move away from the work piece during the start of the next cutting stroke. By rotating the counterweight 114 in the clockwise direction R, a user can more easily initiate cuts into a work piece and significantly reduce the amount of time required to cut through the work piece.

FIG. 5 is a graph depicting vibrations generated by the reciprocating saw 10 in a vertical direction during operation, while FIG. 6 is a graph depicting vibrations generated by a reciprocating saw including a counterweight that is rotated in an opposite direction than the counterweight 114 discussed above. As shown in FIG. 5, the velocity of the saw 10 lags its acceleration. Thus, the velocity of the clockwise-rotating saw 10 counterweight 114 is downward at the end of the return stroke and at the beginning of the cutting stroke. This downward velocity results in a force that drives the saw 10, and more particularly the saw blade 112, into a work piece to start cutting the work piece. In contrast, the velocity of a counterclockwise-rotating saw 10, as depicted in FIG. 6, results in a force that drives the saw 10 and the saw blade 112 upward at the end of the return stroke and at the beginning of the cutting stroke. With the arrangement depicted in FIG. 6, the saw and saw blade are pulled away from a work piece at the start of each cut, which may cause the saw to “jump” and reduce cutting efficiency.

With reference to FIG. 7, in some embodiments, the reciprocating saw 10 further includes a rotation direction reversal switch 134 for reversing a rotational direction of the motor 18. Reversing the rotational direction of the motor 18 causes the counterweight 114 to reverse directions along the path P (i.e., to change direction between the clockwise direction R and the counterclockwise direction). The rotation direction reversal switch 134 is supported by the housing 14 and actuable by the user to selectively reconfigure the motor 18 between a forward mode (corresponding to rotation of the counterweight 114 in the clockwise direction R) and a reverse mode (corresponding to rotation of the counterweight 114 in the opposite, counterclockwise direction). In this way, the user may select a cutting mode (i.e., forward or reverse, corresponding to clockwise or counterclockwise rotation of the counterweight 114) most amenable to the particular characteristics of the work piece to be cut (e.g., material strength, hardness, etc.), and thereby improve the cutting performance of the reciprocating saw 10.

In the illustrated embodiment, the reversal switch 134 is supported by the rearward portion 26 above the D-shaped handle 42. In other embodiments, the reversal switch 134 may be supported at other regions of the housing 14, such as at the handle 42 itself, or adjacent the battery support portion 34. In some embodiments, the reversal switch 134 may be configured as a slide switch and may be actuable between a forward position corresponding to the forward mode (i.e., rotation of the counterweight 114 in the clockwise direction R along the path P of FIG. 12), and a reverse position corresponding to the reverse mode (i.e., rotation of the counterweight 114 in the counterclockwise direction). In other embodiments, the reversal switch 134 may be a dial, a push button, or other suitable actuator. The housing 14 may include indicia (e.g., letters or symbols) adjacent the reversal switch 134 to help identify the current position of the switch 134 and, thereby, the mode of the motor 18.

FIG. 8 is a block diagram of a control mechanism 138 associated with the reciprocating saw 10. The control mechanism 138 includes a controller 142 that is electrically and/or communicatively connected to a variety of components of the reciprocating saw 10. For example, the controller 142 is connected to the motor 18, a power supply 146 (e.g., the battery pack or the power cord discussed above), the trigger 50, a speed switch 150 for adjusting a rotational speed of the motor 18, and the rotation direction reversal switch 134.

The controller 142 includes, among other things, a processing unit 154 (e.g., a microprocessor, a microcontroller, or another suitable programming device) and memory 158. The memory 158 can include, for example, a program storage area and a data storage area. The processing unit 154 can be connected to the memory 158 for execution of software instructions that are capable of being stored in a RAM of the memory 158 (e.g., during execution), a ROM of the memory 158 (e.g., on a more permanent basis), or another non-transitory computer readable medium such as another memory or a disc. Actuating the reversal switch 134 may, for example, reverse the polarity of the motor 18 via the controller 142.

As discussed above, the arrangement of the counterweight 114 and the driven gear 74 influences cutting performance of the reciprocating saw 10. That is, in operation of the reciprocating saw 10, when the counterweight 114 is rotated along a path P in a clockwise direction R (when viewing the reciprocating saw 10 as shown in FIG. 2) the mass portion 122 of the counterweight 114 tends to drive the reciprocating saw 10 and the saw blade 112 into the work piece at the start of the cutting stroke. In contrast, when the counterweight 114 is rotated in the opposite direction (i.e., counterclockwise when viewing the reciprocating saw 10 as shown in FIG. 2), the reciprocating saw 10 and the saw blade 112 may tend to move away from the work piece during the start of the cutting stroke.

Additionally, when the saw 10 operates in the forward mode, the clockwise rotation of the counterweight 114 tends to increase a proportion of vibration experienced by the saw blade 112 in a vertical direction that is generally transverse to the front-to-back direction along which the saw blade 112 reciprocates. The forward mode of operation of the saw 10 tends to improve cutting performance in relatively softer materials (e.g., wood) as compared to operating in the reverse mode. Conversely, when the saw 10 operates in the reverse mode, the counterclockwise rotation of the counterweight 114 tends to decrease a proportion of vibration experienced by the saw blade 112 in the vertical direction. The reverse mode of operation of the saw 10 tends to improve cutting performance in relatively harder materials (e.g., metals) as compared to operating in the forward mode.

FIG. 9 is a graph depicting cut times recorded for the reciprocating saw 10 operating in the forward mode, for the reciprocating saw 10 operating in the reverse mode, and for a conventional reciprocating saw 162 configured to operate in only one cutting mode. For each saw 10, 162, the graph compares cut times recorded when cutting through a sample workpiece made of wood, and when cutting through a sample workpiece made of metal. Specifically, cut times were recorded for cuts made through a 2 inch by 12 inch board of White Fir lumber, and through a 2 inch diameter metal pipe.

As shown in FIG. 9, when operating in the forward mode, the reciprocating saw 10 recorded the fastest cut time for cutting the sample wood workpiece, as compared to the reciprocating saw 10 operating in the reverse mode and to the conventional reciprocating saw 162. And, when operating in the reverse mode, the saw 10 recorded a cut time for cutting the sample wood workpiece just slightly faster than that of the conventional reciprocating saw 162. In contrast, the reciprocating saw 10 operating in the forward mode recorded the slowest cut time when cutting the sample metal workpiece. However, when operating in the reverse mode, the reciprocating saw 10 recorded the fastest cut time for cutting the sample metal workpiece, as compared to the reciprocating saw 10 operating in the forward mode and to the conventional reciprocating saw 162.

By selectively reversing the motor between the forward and reverse cutting modes according to which mode may be better suited to the characteristics of the particular workpiece, the reciprocating saw 10 exhibits improved cutting speed for both wood and metal workpieces as compared to the conventional reciprocating saw 162.

Although the invention has been described with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention. Various features and advantages of the invention are set forth in the following claims. 

1. A reciprocating saw comprising: a housing; a motor positioned within the housing and configured to operate in a forward mode and in a reverse mode, the forward mode corresponding to rotation of the motor in a first rotational direction, and the reverse mode corresponding to rotation of the motor in a second rotational direction opposite the first rotational direction; a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that is rotated by the motor, the driven gear being vertically-oriented within the housing and having an upper portion and a lower portion, a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke, the output shaft configured to support a tool element, and a counterweight coupled to the driven gear and rotating with the driven gear; wherein when the motor is operated in the forward mode, the counterweight moves through the upper portion of the driven gear during the cutting stroke of the output shaft, and moves through the lower portion of the driven gear during the return stroke of the output shaft.
 2. The reciprocating saw of claim 1, wherein when the motor is operated in the reverse mode, the counterweight moves through the lower portion of the driven gear during the cutting stroke of the output shaft, and moves through the upper portion of the driven gear during the return stroke of the output shaft.
 3. The reciprocating saw of claim 1, further comprising a rotation direction reversal switch coupled to the motor, wherein the rotation direction reversal switch is operable to selectively switch the motor between the forward mode and the reverse mode.
 4. The reciprocating of claim 3, wherein the rotation direction reversal switch is a manual switch supported by the housing.
 5. The reciprocating saw of claim 1, wherein the driven gear is rotated by the motor about a central axis, and wherein a rotational direction of the driven gear about the central axis is reversed when the motor is switched between the forward mode and the reverse mode.
 6. The reciprocating saw of claim 1, wherein the counterweight includes a connection portion coupled to the connecting rod and a mass portion including a leading edge, a trailing edge, and a curved outer perimeter matching a circumference of the driven gear, the curved outer perimeter extending more than 90 degrees between the leading and trailing edges.
 7. The reciprocating saw of claim 1, wherein the housing includes a battery support portion, wherein the motor rotates about a motor axis that extends through a center of the driven gear to divide the driven gear into the upper portion and the lower portion, wherein output shaft is located on a same side of the motor axis as the upper portion of the driven gear, and wherein the battery support portion is positioned on the same side of the motor axis as the lower portion of the driven gear.
 8. A reciprocating saw comprising: a housing; a motor positioned within the housing, the motor including a pinion, and the motor being configured to operate in a forward mode and in a reverse mode, the forward mode corresponding to rotation of the motor in a first rotational direction, and the reverse mode corresponding to rotation of the motor in a second rotational direction opposite the first rotational direction; a rotation direction reversal switch supported by the housing and coupled to the motor, the rotation direction reversal switch operable to selectively switch the motor between the forward mode and the reverse mode; and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that engages the pinion and is rotated by the motor, the driven gear being vertically-oriented within the housing, a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, an output shaft coupled to the connecting rod to reciprocate relative to the housing and configured to support a tool element, and a counterweight coupled to the driven gear and rotating with the driven gear.
 9. The reciprocating saw of claim 8, wherein the driven gear has an upper portion and a lower portion, and wherein when the motor is operated in the forward mode, the counterweight moves through the upper portion of the driven gear during a cutting stroke of the output shaft, and moves through the lower portion of the driven gear during a return stroke of the output shaft.
 10. The reciprocating saw of claim 9, wherein when the motor is operated in the reverse mode, the counterweight moves through the lower portion of the driven gear during the cutting stroke of the output shaft, and moves through the upper portion of the driven gear during the return stroke of the output shaft.
 11. The reciprocating saw of claim 8, wherein the rotation direction reversal switch is manually operable.
 12. The reciprocating saw of claim 8, wherein the driven gear is rotated by the motor about a central axis, and wherein a rotational direction of the driven gear about the central axis is s when the motor is switched between the forward mode and the reverse mode.
 13. The reciprocating saw of claim 8, wherein the counterweight includes a connection portion coupled to the connecting rod and a mass portion including a leading edge, a trailing edge, and a curved outer perimeter matching a circumference of the driven gear, the curved outer perimeter extending more than 90 degrees between the leading and trailing edges.
 14. The reciprocating saw of claim 8, wherein the housing includes a battery support portion, wherein the motor rotates about a motor axis that extends through a center of the driven gear to divide the driven gear into an upper portion and a lower portion, wherein output shaft is located on a same side of the motor axis as the upper portion of the driven gear, and wherein the battery support portion is positioned on the same side of the motor axis as the lower portion of the driven gear.
 15. The reciprocating saw of claim 8, wherein the pinion is positioned between the driven gear and the counterweight.
 16. A method of operating a reciprocating saw, the reciprocating saw including a housing, a motor positioned within the housing and configured to operate in a forward mode and in reverse mode, a rotation direction reversal switch supported by the housing and coupled to the motor, and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that is rotated by the motor and vertically-oriented within the housing, a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke, and a counterweight coupled to the driven gear and rotating with the driven gear, the method comprising: operating the reciprocating saw with the motor set in the forward mode; actuating the rotation direction reversal switch to set the motor in the reverse mode; and operating the reciprocating saw with the motor set in the reverse mode.
 17. The method of claim 16, further comprising actuating the rotation direction reversal switch to set the motor in the forward mode.
 18. The method of claim 16, wherein operating the reciprocating saw with the motor set in the forward mode includes moving the counterweight through an upper portion of the driven gear during the cutting stroke, and moving the counterweight through a lower portion of the driven gear during the return stroke.
 19. The method of claim 18, wherein operating the reciprocating saw with the motor set in the reverse mode includes moving the counterweight through the lower portion of the driven gear during the cutting stroke, and moving the counterweight through the upper portion of the driven gear during the return stroke.
 20. The method of claim 19, further comprising cutting a wood workpiece while operating the reciprocating saw with the motor set in the forward mode, and cutting a metal workpiece while operating the reciprocating saw with the motor set in the reverse mode. 